Stabilization of halohydrocarbons



United States Patent 3 Claims. (Cl. 252-453 This invention relates tothe stabilization of halogenated hydrocarbons and, more particularly, tothe inhibition of the decomposition of trichloroethylene encountered inmetal degreasing.

In vapour degreasing operations, trichloroethylene is continuouslyboiled and is thus subject to heat andfcontamination from the metalparts being degreased. This contamination is usually caused by metalchips, water, cutting oils, buifing compounds and vthe like, normallyused in metal machining operations.

Under these conditions, trichloroethylene undergoes decomposition veryrapidly with the formation of acidic compounds which are corrosive tothe degreasing equipment and also act as catalysts for the furtherdecomposition of the solvent.

It has long been common practice to add stabilizers to trichloroethylenedegreasing solvents and, in particular, organic amines have long beenused for this purpose. More recently, it has been claimed, for examplein United States Patent No. 2,797,250, that there exists a synergisticcombination of amines with certain organic epoxides, and that thiscombination is especially effective in stabilizing trichloroethyleneagainst decomposition and acid formation by heat.

As far as is known, it has not hitherto been suggested I that organicquaternary ammonium compounds should be used as stabilizers forhalogenated hydrocarbon degreasing solvents. It has now been discoveredthat these compounds'can be used in extremely effective stabilizingsystems; not, indeed, by themselves, but in a synergistic relationshipwith other known stabilizers. t

It is thus an objectof this invention to provide a new method ofstabilizing halogenated hydrocarbon degreasing solvents. A furtherobject is to provide such solvents stabilized by a new three componentstabilizing system, with or without other known stabilizers. Additionalobjects will appear hereinafter.

The new method of this invention comprises incorporating withhalogenated hydrocarbon degreasing solvents at least one organic aminein an amount between 0.0005% and 0.2% by weight, at least one volatileepoxy compound in an amount between 0.01% and 1.0% by weight and atleast one organic quaternary ammonium compound in an amount between0.0005 and 0.2% by weight.

, The stabilizing method of this invention applies to all The volatileepoxy compounds suitable for the purpose of this invention contain thethree membered epoxy ring:

and must be of a molecular weight such that they retain at least someVolatility at the boiling point of the solvent but are not so volatileas to escape from the degreasing system. Suitable epoxy compoundsinclude propylene oxide, butylene oxide, styrene oxide, cyclohexeneoxide, epichlorhydrin, the 2-methylbutene oxides, butadiene dioxide,hexylene, heptylene and octylene oxides, a-methylstyrene oxides,a-pinene oxide, limonene monoxide and limonene dioxide. They aresuitably used in an amount between 0.01% and 1.0% by weight.

The suitable organic quaternary ammonium compounds have the formula:

wherein the substituents R are not necessarily all the same and normallyrepresent alkyl or alkenyl groups having up to 20 carbon atoms which maycontain branched chains or non-functional substituents that do noteffect the quaternary character of the salt. At least one R may also bean aromatic group, as in benzyl trimethyl ammonium salts. In additiontwo or more R substituents may together with the nitrogen atom. form acyclic aliphatic or aromatic structure, as in dimethyl piperidiniumbromide and cetyl pyridinium bromide. The anion X may be hyrdoxyl, or ahalide anion such as the fluoride, chloride, bromide or iodide anion, oran organic or inorganic acid anion such as the acetate, nitrate, orsulphate anion. The quaternary compounds should be present in an amountbetween 0.005% and 0.2% by weight.

It can thus be seen that a very large number of quaternary ammoniumcompounds can each successfully be used as one member of the stabilizingsystem of this invention. An exhaustive list of said compounds would beof encyclopaedic :dimensions, and thus the compounds have been definedby reference to the above formula.

The synergistic -efiect of the three essential ingredients of thestabilizing system will be demonstrated by the following exampleswherein it .is shown that the three together are far more effective thaneach singly or any two together. However, it has also been found that afurther improvement can be obtained by adding to the system other knownstabilizers such as N-methyl pyrrole V or isopropan-ol; Thus, theinvention includes degreashalogenated hydrocarbons used as vapourdegreasing solvents and, particularly, chloroform.

The organic amine used as one member of the new stabilizing system ofthis invention may be any basic amine such as the pyridines or.picolines, or straight or branched chain aliphatic or aromatic aminessuch as triethylamine, diisopropylamine, aniline, dimethyl aniline orN-alkyl morpholines. The necessary properties of the amine stabilizerare: (1) it must be soluble in the solvent, (2) it must possesssufficient volatility to be distilled with the solvent, and (3) it mustreact with HCl in chlorinated hydrocarbon solution. Suitable amounts ofamine range from about 0.0005 to 0.2% by weight of the solvent; thelower amounts (below 0.001%) are usually useful only in the presence ofother stabilizing species, such as N-methyl pyrrole, discussedhereinafter.

to trichloroethylene and methyl ing solvents containing not only thethree essential synergistic stabilizers, but also the three togetherwith one or more other known stabilizers. The resulting level ofstability is far above that required in the great majority of industrialdegreasing applications, but it may be found to be economical to sellonly one grade of highly stable solvent to all users in order to copewith the few who need the highest available stability.

The examples only illustrate the invention by means of specificmodifications and the invention is not limited to these modificationsbut only by the appended claims. In all the examples the test procedurewas the follow ing. A pH measuring was used consisting of a 500 ml.flask, a reflux condenser and a glass Water trap located between thecondenser and the flask. Two pH electrodes dipped into this water andwere connected to a recorder. Trich-loroethylene (as a typical solvent,except in Example 6) was boiled in the flask and the condensate allowedto fiow continuously through the water layer so that changes in the pHof the solvent were passed on o the water layer and a continuous recordof the solent pH obtained. In order to accelerate the decompoition ofthe solvent it was exposed to ultraviolet light ind oxygen was bubbledthrough the liquid which conained samples of iron wire and a cuttingoil. The ex- Jeriments involved recording the time for the pH tolecrease to 7 and then, usually quite rapidly, to 5. In 1. commercialdegreaser a pH of 7 is critical, while a )H of begins to cause seriouscorrosion and approaches he point where the violent condensationreaction of trizhloroethylene starts.

4 Example 2 Percent Component 5, isopropan-ol 0.004 Component 6,N-methyl pyrrole 0.01

and Component 7, diisobutylene 0.15

It can be seen, however, that the omission of any one of the threeessential synergists destroys the solvent stability despite the presenceof the extra stabilizers (3 and 4 are alternative quaternaries).

TABLE III Stabilizing Component Hours to pH 7 Hours to pH 5 1 l 2 l 3 45 6 7 X X X 12% 13% 14 13% X X X 21% 16% 22% 17% X X X X X pH of 8.2after 24 hrs.

X X X 6% 6% 7% 7 X X X X 4% 3% 4% 4 X X X X X 3% 5% 7 8 X X X c. X X 2536% 27% 39% X X X X X 58% 57 67% 64% Example 1 3O Suitable amounts ofcomponents 5, 6 and 7 are respec- Table I demonstrates the essentialsynergistic action of the three components the presence of which isindicated by an X in the first column. Component 1 is butene oxide(0.25% by weight), component 2 is triethylamine (0.0025% by weight) andcomponent 3 is cetyl trimethylammonium bromide (0.002% by weight) Thelast example in Table I is within the scope of this invention.

Each experiment was conducted in duplicate. Since the decomposition isautocatalytic, it has been found that a system which stabilizes for 10hours is much more than twice as effective in commercial use as onewhich does so for only 5 hours.

TABLE I Stabilizing Component Time to pH 7 Time to pH 5 in hours inhours X A X 5% 1 X X 3% 4% 3% X X 7% 6% 8% X X 12% 13% 14 13% In TableII, similar results are presented wherein the quaternary component 4 isa trimethyl ammonium chloride wherein the fourth alkyl substituent isthe residue of coconut fatty acids, and is sold commercially as Arquad C(Armour Chemical Co.).

TABLE II Stabilizing Component Time to pH 7 Time to pH 5 in hours inhours X 4% 5% X 2% 3% 4 3% X X 18 1s 19% 19% -In Table III, results areshown showing the beneficial eflect of the addition of other stabilizingcomponents, in particular:

tively .00'1%-1.0%, .002%-1.0%, and .05%1.0%. It must be emphasized,however, that their use is optional.

Example 3 In Table IV, the effect of further quaternary ammoniumcompounds in the stabilized solvents of this invention is shown. Eachsample contained components 1 and 2, and the particular quaternary usedis named.

It is to be noted that the quaternary ammonium salts need not be addedas such to the solvent but may be prepared in situ. This is most readilyaccomplished by adding an alkyl halide and an amine to the solvent, theamine being possibly already present as component 2, and optionally moreof it being added to react with the alkyl halide. This method of makingthe quaternary ammonium salts has the advantage that the two componentsdistill separately from the sump of a degreaser and form thequaternaries after condensation in the degreasing system. Thus the onlydisadvantage of the quaternary stabilizers, i.e. their non-volatility,is overcome. In practice it has been found, however, that there issuflicient splash-over, in the rudimentary stills used in degreasingplants to separate the grease from the solvent, that suffi cient of evena non-volatile quaternary gets back to the degreaser.

Example 4 In the Table V are shown the results of experiments whereinalkyl halides were used to react with amines to produce the quaternariesin situ. In each case 0.25% by weight of butene oxide (component 1) wasadded.

TABLE V Amine I Alkyl Halide, I Hours to the same pH in the absenceComponent, 0.002% Hours to pH 7 Hours to pH of the halide Percent0.00408 TEA Biii l chloride 6% 8% 9 11% 3% 4 i 0.0020 TEA Butyl iodide7% 5 /2 6% 4 4%} 6 /2 5 0 00282 DMA 5% 7% 7 8% 54 g' it iit' fitiitfiiz1; 3 I: :1 J3: 010047 DIPA: II Butyl chloride- I 10 9% 11% 10/. 4% 5% 5%0% TEA =triethylamine. DMA cliinethylaniline. DIPA diisopropylaminc.

It is apparent from Example 4 that a wide range of Stability: alklyhalides may be used with an amine to function as Hours to pH 7 2 /2 amember of the stabilizing system, apparently by pro- Hours to pH 5 6 /2ducirig a quaternary ammonium compound in situ. Any In the absence ofArquad C: alkyl monohalide will work, but those of such high vola- Hoursto pH 7 1 tility as to be rapidly lost from a degreaser are of littleHours to pH 5 1% practical use. Those whose boiling points are similarto What I claim is: that of the haiogenated hyqmcarbon degrerflsing 9 1.A degreasing solvent selected from the group conam preferred smce theydlstln m the j n pot sistiiig of trichloroethylene and methyl chloroformhaving of a degreaser and reform the active stabilizer. Suitableincorporated therein (1) between 0 0n05% and 0.2% by amounts of hahdebetween and 02% by Weight of at least one amine selected from the groupcon- Welght- The fOHQWmg examgles i f' eflectlve sisting oftriethylamine, dimethylaniline and diisopropylness of butyl chloride(3.1. 78 C.) mthis use. amine, (2) between 001% and 1.0% by weight of atleast one vic-epoxy compound selected from the group Example 5consisting of butylene oxide and styrene oxide, and (3) between 0.0005%and 0.2% by weight of at least one A c0nib.nation of two epoaides wasused, and this is quaternary ammonium Compound Selected from the in somecases to be preferred. The stability tests were y group consisting ofcetyl trimethyl-arnrnonium bromide, run as in previous examples, and thesolvent for distillab1 t th 1 h d t t th 1 tion was mixed with 30% bywcivht of cuttin oil and CG ammonium? y e we y d rnoiiium iodide,coco-trimethyl-ammonium chloride, dlsnnefi at a tel-Immature not 121 hcoco-triniethyl-ammonium acetate and coco-trimethyllatter 15 thatavailable from 15 p.s.i.g. steam, used in ammonium hydroxide mostplants. The tiichloroethylene was steam stripped l A degreasing SolvantSelected from the group Cork from the Tesldue and added t0 thedlstlllatesisting of trichloroethylene and methyl chloroform hav iiigincorporated therein (1) between 0.0005 and 0.2% TABLE VI by weight ofat least one amine selected from the group consisting of triethylamine,dimethylaniline and diiso- I Samplel SamplcZ propylainine, (2) between0.01% and 1.0% by weight of at least one Vic-epoxy compound selectedfrom the Stabilizers in wt. percent: group consisting of butylene oxideand styrene oxide, g ;g% g 3;? 8% and (3) be ween 0.001% and 0.2% byWeight of at least Triethylaininc. 0. 00 one alkyl monohalide selectedfrom the group consisting g jggrggsg tggff M04 3-331 of butyl chloride,butyl bromide, butyl iodide and cetyl Stability before distillation: 8yW W my iodide. I

E335; E8 3% gjjjjjjjjjjjjjjjjj 9 2 2 gyj 12 2 3. Adegreasing solvent asclaimed in claim 1 contain Stability after distillation: 1 9 mgadditionally a stabilizing amount of at least one comg jj j j j 3 3 10pound selected from the group consisting of isopropauol,

N-methyl pyrrole and diisobutylene.

References Cited by the Examiner Example 6 UNITED STATES PATENTS Similarexperiments on another chlorinated hydrocar- 2,435,312 2/ 1948 Klabunde260 652 5 bon degreasing solvent, namely methyl chloroform, gl b ltnde uope in showed similar advantageous res Its 2, 7 92 2/1961 Graham 260652'5 Stabilizers: Amount in percent by wt. 3,000,973 1 1 Fre enburg260-652.5

.25 ifil fii zfiff jjjjjjjj ,8325 E N TVER. m y Ex miner. Arquad C 0.002ALPHONSO D. SULLIVAN, DANIEL D. HQRWITZ,

Examiners.

1. A DEGREASING SOLVENT SELECTED FROM THE GROUP CONSISTING OFTRICHLOROETHYLENE AND METHYL CHLOROFORM HAVING INCORPORATED THEREIN (1)BETWEEN 0.0005% AND 0.2% BY WEIGHT OF AT LEAST ONE AMINE SELECTED FROMTHE GROUP CONSISTING OF TRIETHYLAMINE, DIMETYLANILINE ANDDIISOPROPYLAMINE, (2) BETWEEN 0.01% AND 1.0% BY WEIGHT OF AT LEAST ONEVIC-EPOXY COMPOUND SELECTED FROM THE GROUP CONSISTING OF BUTYLENE OXIDEAND STYRENE OXIDE, AND (3) BETWEEN 0.0005% AND 0.2% BY WEIGHT OF ATLEAST ONE QUATERNARY AMMONIUM COMPOUND SELECTED FROM THE GROUPCONSISTING OF CETYL TRIMETYL-AMMONIUM BROMIDE, CETYL TRIMETHYL-AMMONIUMACETATE AND COCO-TRIMETYLAMMONIUM HYDROXIDE.